Hi Arvind,
I completely agree with the comment from David, I would also recommend do
use use "-g -Os" by default and "-g -O1" if you struggle while debugging.
Regarding the binary size, I have recently played around with the TI/RedHat
GCC release and the results are IMO really really bad (standard library??):
==============================================================================||
|||| CODE SEGMENT SIZE (in kB)
||||
||||============================================================================||||
BENCHMARK NAME | COMPILER VERSION | -Os | -O2 |
-O3
||||=====================+========================+=========+=========+=========||||
Dhrystone v2.1 | mspgcc v4.7.2 | 5.81 | 5.79 |
5.81 |||| (common version) | msp430-elf v4.9.1 | 36.60 |
37.10 | 37.11
||||---------------------+------------------------+---------+---------+---------||||
Dhrystone v2.1 | mspgcc v4.7.2 | 5.70 | 5.67 |
5.69 |||| (MCU adapted) | msp430-elf v4.9.1 | 36.61 |
37.08 | 37.10
||||---------------------+------------------------+---------+---------+---------||||
CoreMark v1.0 | mspgcc v4.7.2 | 10.48 | 11.26 |
16.22 |||| (official version) | msp430-elf v4.9.1 | 41.43 |
42.43 | 49.24 ||
==============================================================================
More about that in this thread:
https://groups.google.com/forum/?fromgroups#!topic/discuss_openmsp430/W-22HePtJsQ
Cheers,
Olivier
On Thu, Feb 19, 2015 at 9:13 AM, David Brown <da...@westcontrol.com> wrote:
> On 19/02/15 06:10, Arvind Padmanabhan wrote:
> > Hi Folks,
> >
> > My friend has Code Composer Studio (CCS) license. He compiled without
> > debugging and no optimization. Code size (ROM) is only 35 KB. This is
> > good for MSP430G2955 that has 56 KB of Flash.
>
> There is no standard for how much optimisation a compiler does -
> settings are only relative to each other in a given compiler. Sometimes
> you can compare /types/ of optimisation pass between compilers, but even
> then the details vary wildly.
>
> When gcc is used with -O0 (or no optimisation flags), it produces blind
> statement-at-a-time interpretation of the code that is very big, very
> slow, and very hard to follow. Apart from some tests of the compiler
> itself, it is pretty much useless.
>
> With -O1, you get little in the way of code reordering and no inlining
> without the "inline" keyword, but variables go in registers and there is
> some basic simplification. If you want the easiest single-step
> debugging, "-O1 -g" works much better than "-O0 -g" because you have
> clearer and more logical assembly code.
>
> With -Os (or -O2), you get a lot more re-arrangement of code, which can
> give smaller and faster results but sometimes means that single-stepping
> jumps around, and breakpoints don't always appear where you expect them
> (a trick here is to make artificial volatile variables, and put
> breakpoints on lines that use them).
>
> -O3 and other options are a more specialised, and can sometimes make
> code faster, sometimes slower.
>
> With CCS, it's "no optimisation" setting would rate around 0.8 on gcc's
> scale, while it's fullest optimisations are around 1.8 (varying by the
> actual code in use, of course).
>
>
> >
> > I compiled the same code using mspgcc, I get the following (-g -Oo):
>
> So use "-g -O1" or "-g -Os".
>
> Unless you have something you need to step through carefully (in which
> case use "-g -O1", it is best to use exactly the same settings ("-g
> -Os") all the time - that way you are debugging what you are going to
> release, and releasing what you have debugged.
>
> >
> <snip>
> > If I remove -g option and optimize for size (-Os), then I can get it
> > down to 32 KB. Problem is I can't do debugging in this case. Am I
> > missing some trick or is CCS compiler doing something smart?
> >
> > Regards, Arvind
> >
> >
>
>
>
>
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